1. Field of the Invention
The present application relates to a fuel supply apparatus for an engine.
2. Discussion of the Background
In the related art, there are engines having a fuel injection valve installed on each cylinder of a multi-cylinder engine. For example, in some V-type engines or horizontally opposed engines, two rows of cylinders are provided, and a single fuel supply passage from a fuel tank (fuel pump) branches out to each of delivery pipes extending in the direction of the corresponding cylinder row (see, for example, Japanese Unexamined Patent Application No. 2004-132231).
In engines with a fuel injection valve installed on each cylinder, injection of fuel produces a pressure pulsation in each delivery pipe. Further, in the case of engines having a pair of cylinder rows such as V-type engines or horizontally opposed engines, the pressure pulsation may induce vehicle vibration or noise, or may lead to deterioration of fuel economy or emission increases due to unstable combustion resulting from inability to obtain a desired pressure for the fuel in the fuel supply pipe.
In Japanese Unexamined Patent Application No. 2004-132231 mentioned above, a pair of connecting pipes each connected to the corresponding delivery pipe are connected to a single fuel supply pipe connected to the fuel pump, in a T-shaped configuration. The pair of connecting pipes extend in opposite directions coaxially in the same straight line. Such a piping structure has a problem in that the pressure pulsation is amplified along the axial direction of the pair of connecting pipes.
In the case of V-type engines, in particular, the direction of vibration differs between the two cylinder rows. Accordingly, the impact of vibration on the delivery pipes, the connecting pipes, and the fuel supply pipe, and also the connecting portion between the fuel supply pipe and each connecting pipe needs to be taken into consideration.